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Intel Core i7 920 Overclocking

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Hard Hat Area March 2009 • Vol.9 Issue 3 Page(s) 52-55 in print issue

Intel Core i7 920 Overclocking Push Nehalem To Its Limit

The 2.66GHz Core i7 920 is currently the least expensive model available in Intel’s Core i7 desktop processor lineup. At about $300 online, it’s approximately $700 cheaper than the flagship Core i7 965 Extreme.

When it launched its Core i7 desktop processors, Intel called it the biggest platform architecture change in the company’s history to date. Although the Pentium 4 and Core 2 processors respectively ushered in the NetBurst and Core microarchitectures, neither necessitated an entire platform shift like Core i7 did. With the Nehalem microarchitecture, on which the Core i7 is based, new features and functionality inherent in the design required Intel to essentially revamp its entire desktop platform.

Along with the Core i7 line of processors came motherboards built around a new chipset, the X58 Express, with a new 1,366-pin socket. Because Intel incorporated triple-channel DDR3 memory and specialized power management controllers into the Core i7’s die and outfitted the processors with a new cache structure and reworked HyperThreading engine, the chips needed more power and data paths than the trusty Socket LGA 775 could provide. And because Core i7 processors no longer had to interface with a separate memory controller hub in a Northbridge chip, the FSB was axed in favor of a new serial interface, dubbed QPI (Quick Path Interconnect).

All of the changes brought forth by the Core i7 meant overclockers have had a host of fresh intricacies to become familiar with if they wanted to wring the most performance from the new platform. Although there are a plethora of new terms to digest with the Core i7, thankfully it turns out tweaking and overclocking Intel’s new baby is fairly straightforward. It also turns out that the Core i7 has plenty of headroom left, even at this early stage of its lifecycle.

Overclocking Considerations

To show you just what the new Core i7 is capable of, we decided to put Intel’s “entry-level” Core i7 processor, the 920, through the wringer and overclock it as far as we could. Although the Core i7 920 is the least expensive processor in the Core i7 lineup, at about $300, it’s still somewhat pricey by today’s standards. Factor in a good motherboard and triple-channel DDR3 memory kit, and we’re talking another $400 to $550, on top of the investment required for the CPU. That’s a significant outlay for most of us, so we decided to keep things relatively simple and tweak our Core i7 920 using Intel’s stock cooler to illustrate what it could do without investing even more in an exotic, more expensive, cooler.

Before we dig into the specifics, however, there are some special considerations to make when overclocking a Core i7 processor. For one, only the Core i7 965 Extreme is unlocked. That means the Core i7 920 we’ll be using (as well as the Core i7 940), must be overclocked through some other means—we’ll explain what that is in a little while. Core i7 processors also feature Turbo mode, which increases the CPU’s frequency slightly if it’s running within acceptable thermal limits. This is important to remember, because Turbo mode may push the ultimate processor frequency too high if you also happen to be overclocking the CPU, so it is best to keep Turbo mode disabled on an overclocked system. Typ-ically, you can disable Turbo mode via the motherboard’s BIOS.

Although there are some new considerations to make when overclocking a Core i7 processor, some tried-and-true rules still apply. A solid enthusiast class motherboard, such as the Gigabyte GA-EX58-Extreme, is a must, as is a good CPU cooler, such as this Thermalright unit.

Core i7 processors also feature Hy-perThreading. HyperThreading can boost performance when heavily multitasking or when running multithreaded applications, but it can also make it somewhat harder to overclock. To hit the absolute limit with a Core i7, it helps to disable HT. We think the performance benefits of Hyper-Threading are worthwhile though, so we left it enabled for this project. We’d gladly sacrifice a few MHz for the addition of four logical processor cores.

Voltage (or, more specifically, memory voltage) is also a consideration when overclocking the Core i7. Intel recommends a memory voltage no higher than 1.65V to prevent damage to the CPU’s integrated memory controller. Higher voltages are an option (and we personally haven’t killed a Core i7 yet using memory voltages as high as 1.8V), but if Intel re-commends staying at or below 1.65V, there is a good reason. To prevent unnecessary damage, we’d recommend using a memory kit specifically designed for the Core i7 and capable of high frequencies without needing more than 1.65V.

Finally, there is the BCLK (base clock) to consider. The ultimate frequency of a Core i7 processor, its QPI link, and its memory speed are all derived from a BCLK frequency, which is set to 133MHz by default. Although the FSB is no more, it may help to think of the BCLK frequency as similar to the FSB clock. Raising the BCLK raises the CPU clock, QPI speed, and memory speed in lockstep. To keep all things running within stable limits, most X58-based motherboards for the Core i7 give users the ability to alter QPI and memory multipliers independently of the CPU, QPI, and memory clocks. All can be fine-tuned to some degree. Raising the base clock is how we overclocked our Core i7 920.

Tools Of The Trade

We overclocked our Core i7 920 processor by altering a few options in our motherboard’s system BIOS. To achieve our final processor frequency of 3.8GHz (an increase of 42.5%) we increased the CPU Vcore, QPI, and DRAM voltages, dropped the system memory multiplier, and raised the BCLK (base clock) frequency.

We began our Core i7 920 overclocking project by assembling our system in an open-air test bench to ensure excellent cooling. The main parts consisted of a Core i7 920, Gigabyte GA-EX58-Extreme motherboard, and a triple-channel Qimonda DDR3-1066 memory kit. As is always the case when overclocking, adequate cooling and high-quality components are a must. Because we wanted to focus on the CPU frequency for the purposes of this article, we went with Gigabyte’s flagship X58 Express-based motherboard, which is an excellent overclocker, but stuck with an affordable memory kit. For a higher memo-ry overclock, a more expensive DDR3-1333 or 1600 triple-channel kit would be a better choice.

Making The Mods

All of the modifications that were necessary to overclock our Core i7 920 processor were made from within the system BIOS. We began by disabling Turbo mode and increasing a few key voltages. As we mentioned earlier, Core i7 processors are sensitive to memory voltage, so we only kicked that up to 1.66V. We weren’t planning to push the memory too far, so increasing the memory voltage further wasn’t necessary. Then we raised the CPU core voltage up from its default of 1.25V to 1.35V and gave the QPI voltage a slight bump from 1.15 to 1.18V.

Next, we began to increase the BCLK frequency in 10MHz increments un-til the system was no longer stable. Throughout the process, we also lowered the memory frequency to keep it running as close to 1,066MHz as possible. We were able to boot into Windows with a BCLK frequency of 193MHz, which resulted in a 3.86GHz CPU clock (20 x 193MHz), but the system wasn’t completely stable. It would boot into Win-dows, but some benchmarks, such as Cinebench, would crash to the Desktop. So, we slowly began lowering the base clock and ultimately settled on a BCLK of 190MHz, producing an even 3.8GHz CPU clock. At these speeds, our memory was running at 1,140MHz, and the QPI frequency was at 6.8GTps.

The Final Countdown

A final clock speed of 3.8GHz was an increase of approximately 1.1GHz over the Core i7 920 processor’s default frequency and well above the Core i7 965 Extreme’s default clock of 3.2GHz. That is an excellent overclock for a brand new CPU using a stock cooler. Keep in mind, as the Core i7 matures, higher clock speeds may be possible; a more powerful cooler would have likely improved our immediate results, as well. Of course, there’s no guarantee that every Core i7 920 processor will overclock as well as ours, but early indicators show a lot of promise. With that said, 3.2 to 3.4GHz should be a very real possibility for most chips, which would put this $300 CPU on par with Intel’s best.

by Marco Chiappetta

Intel Core i7 920 Performance: Before & After The Mod


There’s no point in overclocking a system and potentially voiding a slew of warranties in the process if there’s no reward for the effort. To illustrate just how rewarding it was to overclock our Core i7 920 processor, we ran a handful of benchmarks on our test machine with the CPU running in its stock form and while overclocked. For reference and comparison, we also ran a Core i7 965 Extreme processor through the same battery of benchmarks and compared all of the results in the chart seen here.

The common components in our test system consisted of a GeForce GTX 280 graphics card, Gigabyte GA-EX58-Extreme motherboard, Western Digital 150GB Raptor hard drive, Ultra 1kW PSU, Lite-On DVD-RW drive, and a 3GB triple-channel Qimonda DDR3-1066 memory kit. We ran Windows Vista Ultimate (32-bit) on the system, with Intel’s latest chipset software and Nvidia’s latest video drivers installed.

As the benchmark results show, there was quite a large performance delta that separated the stock Core i7 920 and the 965 Extreme. In every single test, the Core i7 965 Extreme outperformed the stock Core i7 920 by a sizable margin. With our Core i7 920 processor overclocked from 2.66GHz to 3.8GHz, however, the tables were completely turned. Our modded and overclocked system outpaced the Core i7 965 Extreme by margins ranging from 4.66% to as high at 15.63%. We attained the largest gains in more CPU-intensive applications, such as 3D rendering and the synthetic benchmarks; gaming and encoding tests showed the smallest gains.

	Stock Clock SpeedsCore i7 920 @ 2.66GHz	Overclocked Speeds Core i7 920 @ 3.8GHz	Core i7 965 Extreme @ 3.2GHz	Percent Difference (Mod vs. Core i7 965 Extreme)
BCLK Frequency	133MHz	190MHz	133MHz
Memory Frequency	1,066MHz	1,140MHz	1,066MHz
SiSoft SANDRA 2009 SP2 Processor Arithmetic
Dhrystone iSSE4.2	70.47 GIPS	97.56 GIPS	84.88 GIPS	14.9%
Whetstone iSSE3	63.87GFLOPS	82.87GFLOPS	74.61GFLOPS	11.07%
Processor Multimedia
Integer x8 iSSE4.1	126.40 Mpixels/s	169.74 Mpixels/s	148.84 Mpixels/s	14.04%
Floating Point x4 iSSE2	102.25 Mpixels/s	136.41 Mpixels/s	120.23 Mpixels/s	13.45%
Memory Bandwidth (GBps)
Integer Buffered iSSE2	17.43GBps	19.67GBps	18.32GBps	7.36%
Floating Point Buffered iSSE2	17.41GBps	19.66GBps	18.33GBps	7.25%
Futuremark 3DMark06
CPU Benchmark	4895	6187	5562	11.24%
LAME MT MP3 Encoding (minutes:seconds)
Multithreaded	0:29	0:22	0:25	12%
Cinebench R10
Multithreaded	3,248	4,551	3,902	15.63%
Kribibench v1.1 (FPS)
Sponge Explode Model	22.99	30.41	28.17	7.95%
Ultra Model	6.17	8.16	7.28	12.10%
POV-Ray (PPS)
Multithreaded	3,501	4,993	4,340	15.04%
Crysis v1.21 (FPS)
CPU Test (800 x 600, low quality)	164.57	188.24	179.85	4.66%

(Intel Chipset Drivers v9.1.0.1007; Nvidia ForceWare v180.48)

I'm sorry an oced 920 at 3.8GHz is compared to a stock 965 at 3.2GHz?

they could have saved their time, any of us could have told them that a stock 965 beats a stock 920 and an oced 920 at 3.8GHz beats a stock 965 at 3.2GHz.

news flash a 940 OCed to 3.6GHz has been found to beat a stock 920 and beats a stock 965 by about 8 - 10%

I mean this is the whole point of OCing a CPU, so that you can get better performance out of it.

e06028 thank you for the effort and I mean that , unfortunately the source has too much time on their hands and can't find a great way of using it

Edited by DST4ME - 03 Mar 2009 at 4:16am

DST4ME, I agree with your comments, but not everybody is as literate as you with computers.  Now that this topic is here you can post the link in your replies instead of explaining to everyone why they need to get the 920 OC instead of the 940 or 965.  Heck I made it easier on you.

Edited by e06028 - 04 Mar 2009 at 6:13pm